In his Mist Energy System, water is pressurized by a commercially available high pressure pump, it is then released through a nozzle into an impact chamber, where the jet hits a metal target. Heat is released and the water instantly transforms into steam. The energy spent to pressurize the water and pre-heat the impact chamber is about one tenth of the energy contained in the steam that is produced. That is a 10:1 over-unity factor, achieved with nothing but available tech and water as a medium.

See a more detailed explanation in Hydrogen Bond Explosions

Of course steam is what has been driving our electricity-producing machines for a long time. The heat is usually supplied by burning carbon fuels like coal, oil or gas. Even atomic power plants are little more than very expensive - and rather dangerous - steam engines fired by the heat of radioactive elements.

So if we could make the needed steam without recourse to carbon based or atomic fuels, would that not be a giant step forward?